Synthesize, purify, analyze, and supply NCI with sufficient quantities of retinoids for chemoprevention and toxicity studies. The approach will involve the synthesis of quantities of modified retinoids, the choice of which will be dictated by the needs and interest of the NCI Carcinogenesis Program. In general, the contractor will: synthesize a variety of geometric isomers of retinoids; provide assay and analytical data on all compounds; supply NCI Carcinogenesis Research Program with 100 mg of each purified compound; and prepare data sheets describing preparative methods and requirements for handling and storing materials.